Enhanced salt rejection of hydroxylated BaTiO3/Ti3C2Tx@polyvinyl alcohol composite nanofiltration membranes under electrochemical assistance

Abstract

The influence of surface charge density of nanofiltration (NF) membranes could due to enhanced electrostatic interaction through electrically assisted. In this study, the hydroxylated BaTiO3/Ti3C2Tx (HBT)@polyvinyl alcohol (PVA) (HBTA) composite NF membranes were prepared by crosslinking HBT on the surfaces of NF membranes. The optimized HBTA-0.06 sample exhibited a water contact angle of 43.7°, zeta potential of −13.73 mV (pH = 6.5), average effective pore size of 0.319 nm, and pure water permeance of 55.1 L·m–2·h–1. At an applied electric field of 3 V, the rejection rates of LiCl, NaCl, KCl, RbCl, and MgCl2 determined for HBTA-0.06 reached 73.3%, 60.1%, 53.6%, 49.4%, and 59.8%, respectively. HBTA-0.06 has good stabilization properties that are especially advantageous for water purification, indicating good long-term filtration stability within 168 h. Furthermore, HBT doping significantly increased the charge density of the HBTA membranes and the rejection efficiency of chloride salts, both chlorine radicals (·Cl) and hydroxyl radicals (·OH) generation pathways were proposed under electrochemical assistance. Hence, electrical assistance represents a novel and effective technique for enhancing the salt rejection properties of multifunctional composite NF membranes.